Armed forces personnel may be required to perform their respective duties with equipment, including facial gas masks, issued for personal protection in contaminated land, sea, or air environments. Rapid and effective verbal exchange of information is essential for the conduct of operations. All mask designs currently in use for this purpose incorporate one or more voice transmitter assemblies in the form of sealed diaphragms. Other common design characteristics include a nosecup/mouth seal extending from the bridge of the nose, around the mouth and to a chincup. Voice transmission may be directly affected by changes in the design of the nosecup/mouth seal.
Speech transmitters currently fitted into protective masks employ a metal casing which houses a mylar membrane and a specially constructed rubber tension ring to apply a frictional force to the membrane. The tension ring is secured in place by crimping of the entire assembly. Observations have shown that the tensional forces applied to the mylar membrane are not maintained over time resulting in progressive degradation of the quality of speech transmission.
In addition to crimping the assembly, other designs apply tension to the mylar membrane by pulling the edges of the membrane around a radius. Rubber gaskets were introduced to prevent leakage and protect the mylar membrane.
Current designs require a silicone rubber tension ring for each size of speech transmitter. Silicone requires a post curing operation and is relatively expensive. It has been found that mass production of these items has not been possible and, accordingly, costly manual assembly has been required.